Clippers of the type having a fixed cutter with a first row of teeth and a movable cutter with a second row of teeth which reciprocates with respect to the fixed cutter have long been very well known. The rows of teeth of the fixed and movable cutters are substantially aligned and the movement of the movable cutters produces cutting action between adjacent pairs of teeth. Such cutting movement is usually provided from the rotating drive shaft or an electric motor by means of an oscillating linkage.
Some or such clippers have electric drive motors inside their handles with short drive shafts closely adjacent to the movable cutters. Others have remote drive motors with long drive shafts which are extended to a position adjacent to the movable cutters by means of flexible co-axial cables. Both of these types of drive arrangements include an eccentric device at the end of the drive shaft which is engaged with the movable cutter in some manner by an oscillating linkage.
Various mechanical linkages have been used between the eccentric device and the movable cutter. Many devices include a lever which pivots about a fulcrum, usually a fulcrum somewhere midway along the length of the lever. Such levers each have a distal end engagable in a slot of some sort formed in the movable cutter and a proximal end which is engageable by the eccentric device. This invention is an improvement in clippers and in mechanical linkages of this general type.
Such linkages cause a number of problems primarily related to the wear which occurs between the distal ends of such levers and the movable cutters with which they are engaged, during attachment and subsequent use. Even if the distal end of the lever fits the slot in the movable cutter relatively snugly when the device is new, wear on the distal end and/or on the slot itself quickly results in a fit which is not snug. A gap develops and grows between the distal end and the sides of the slot.
This causes noise. The initial noise may not be very loud, but, as wear causes the size of the gap to grow, a loud and annoying noise develops. The noise is caused by the distal end of the lever repeatedly hitting the opposite walls of the slot in the movable cutter. Extended use without changing cutters and levers increases gap between the distal end and the slot walls and increases the noise. Such noise can be particularly troublesome when the clipper is used in grooming pets and other animals.
The noise can be reduced to some extent by using non-metallic parts, such as a non-metallic lever or a lever having a non-metallic distal end. Plastic and fiberglas levers have been used to reduce the noise problem. However, use of such soft materials can tend to increase the rate of wear.
Another significant problem caused by the aforementioned undesirable gap between the lever distal end and the slot is that the range of effective driving movement of the movable cutter is reduced as the gap develops and increases in size. For an increasing portion of each stroke the movable cutter is not being driven. This decreases the cutting efficiency of the clipper.
The aforementioned gap caused or increased by wear can lead to other problems as well. In some cases, breakages of parts can even occur.
Examples of prior art devices of the type described, including some efforts to address the above-mentioned problems, include the following U.S. Pat. Nos.: 4,531,291 (Laube); 2,271,029 (Oster); and 1,528,745 (Lutes).
Oster addresses some of the aforementioned problems by means of a complex lever device having a pivoting end member. Such devices may be expensive and can be prone to breakage. Lutes utilizes a rounded distal end, an approach also mentioned in the Oster patent. Prior attempts to solve these problems have had a number of disadvantages and shortcomings. In summary, the problems associated with wear between the distal end of the oscillating drive lever and the movable cutter which it engages remain essentially unsolved.